|Sunday, 17 September 2006|
In general, projectors are devices that display images by projecting light in accordance with image signals transmitted from image transmitters, such as computers. A projector is provided where an image is generated by an image display device receiving an image data from a personal computer or a video camera and projected on a screen. The projector hence includes an optical system for projection of images. A projector modulates light emitted from a light source based on image data with its light modulation means, such as a liquid crystal panel, and displays a resulting image on a screen. The bright images displayed by these projectors and their ready portability are key aspects of their utility. To achieve bright images, these projectors employ special high-intensity, high-temperature light sources. A projector generally include a light source and an optical system projecting and enlarging an image onto a screen, and is divided into two types, a CRT (cathode ray tube) type and an LCD (liquid crystal display) type. The CRT projector comprises a CRT assembly projecting an image beam, a mirror reflecting the projected beam, and a screen on which the reflected beam is displayed as a picture. The LCD projector comprises an LCD instead of the CRT assembly, wherein the image beam is adjusted in gradation by a liquid crystal and then projected and enlarged. Spatial light modulators of projectors may use tilt mirror devices. One of the tilt mirror devices is a digital micromirror device (DMD). The DMD includes a movable mirror element that reflects light from a light source toward a projector lens or in the direction other than that of the projector lens.
Digital image projectors are widely used to project color images generated from digital signals encoding the images onto the front of a reflective display screen for a conference-room presentation or onto the rear of a semi-transparent diffusive screen of a rear-projection display monitor or a projection television. In recent years, efforts have been made to increase the luminance of images projected by projectors, and, as a result, more and more projectors project highly intensive light to form bright images. Conference sessions, meetings, lectures, and other interactive forums invariably involve presentation materials such as text and graphics on a common display medium such as a projector screen. Traditional presentations have included slide shows, consisting of optical transparencies illuminated by a projector onto a display medium. Current computing technology has enabled software applications for developing media slides, and specialized projectors capable of accepting the video output signal from a PC or laptop and projecting directly onto the display medium. The proliferation of laptops and handheld computers allows a presenter to develop a multimedia presentation on a laptop, for example, and present from the laptop by connecting directly to the projector at the conference site. Generally, a portable multimedia projection system includes a portable housing, a channel tuner supported by the portable housing and a controller disposed within the housing. The image projection device externally project images relative to the portable housing. The controller is electrically coupled to the channel tuner and the image projection device. The controller directs video signals from the channel tuner to the image projection device.
A multimedia projection system employs a broad spectrum light source and optical path components upstream and downstream of the image-forming device to project the image onto a display screen. A typical broad-spectrum light source used in a multimedia projector is a high-intensity discharge (HID) lamp. The light from the HID lamp is collected in a reflector that shapes the light and pushes it forward into the projection optics. Multimedia projectors typically employs reflective light valves, the most common types of these reflective light valve optical arrangements are deflected mirror arrays and reflective liquid crystal light valves. Deflected mirror arrays are very efficient reflectors that do not require polarizers for operation. Reflective liquid crystal light valves are typically fabricated on a silicon substrate and are, therefore, referred to as liquid crystal on silicon (LCOS) light valves. They are much less expensive than reflected mirror devices, but require specialized polarizers for operation. All of the above architectures employ linear polarized light-sensitive devices for receiving light from a randomly polarized light source, reflecting the light off the LCOS light valves, and redirecting the reflected light, depending on its polarization direction or state, either out through a projection lens or back toward the light source. Because LCD displays have significant light attenuation and triple path color light paths are heavy and bulky, portable multimedia projectors typically employ DMD displays in a single light path configuration.